1. Field of the Invention:
This invention relates to further improvement of a thermal response type fluid fan coupling device which was disclosed in Japanese Patent Publication No. 7846/1984 by the applicant of the present invention. This thermal response type fluid fan coupling device is arranged to usually control an engine cooling fan of an automobile for the purpose of constantly supplying a suitable quantity of cooling air to the engine in accordance with the operating condition of an automobile.
2. Description of the Prior Art:
A known fan coupling device of the type described above comprises, as exemplified in FIG. 17, a sealed chamber formed by a cover 23' and a case 23". The chamber is divided by means of a separating plate 24 having a flow-adjusting hole 24' into an oil accumulating chamber 25 and a torque transmission chamber 26 which includes a driving disc 22. A circulated passage 27 which is connected to a pumping function portion formed by a dam 28 which connects the torque transmission chamber 26 side and the oil accumulating chamber 25 side is provided. In the fan coupling device, in order to position at least one of an inlet port 27' and an outlet port 27" of the flow passage 27 above the oil level in the oil accumulating chamber 25 regardless of the attitude of the fan coupling device when the engine stops, the outlet port 27" is disposed in the opened area at the tip portion of an arc-shaped and substantially semicircular groove 29 which communicates with the circulated passage 27 which is provided by a separating wall secured to the inner surface of the oil accumulating chamber 25.
The above described conventional fan coupling device satisfies the object of preventing the accumulating of oil in the torque transmission chamber 26 caused by natural inverse flow from the oil accumulating chamber 25 through the flow passage 27 during the period when an automobile is parked when the circulated passage 27 is submerged under the oil level in the oil accumulating chamber 25. As a result of this, rapid increase in the fan speed as soon as the engine is started and abnormal noise from the fan can thereby be prevented, and effective warming up can be realized even when ambient temperature is low. However, when the engine is stopped with the flow adjusting hole submerged below the oil level in the oil accumulating chamber and a valve of the flow adjusting hole in the separating plate set to open the flow adjusting hole after high temperature usage of the engine has been carried out, a great quantity of oil accumulates in the torque transmission chamber as a result of the natural flow from the oil accumulating chamber through the flow adjusting hole. Consequently, as shown by symbol X in FIG. 18, when the engine is again started, the rotational speed of a follower side fan rises for a certain period of time, and so called uneven rotation of the fan occurs.
An object of the present invention is thus to provide a thermal response type fluid fan coupling device in which the uneven rotation of the fan can be kept to as substantially short a time as possible after the engine is started even when the engine is stopped after high temperature usage. Furthermore, in the thermal response type fluid fan coupling, an assured pumping function can be achieved from the outer circumferential portion of the torque transmission chamber to the circulated passage.
A thermal response type fluid fan coupling device according to the present invention constituted as follows: the inside of a sealed chamber which is supported on a rotational shaft whose tip is provided with a driving disc through a bearing and which comprises a case and a cover having cooling fans on the exterior surface thereof is divided by a separating plate which has an oil flow adjusting hole into an oil accumulating chamber and a torque transmission chamber accommodating the driving disc; a dam is formed between an exterior surface of the driving disc and an inner surface of the sealed chamber for the purpose of introducing oil into a circulated passage connecting the torque transmission chamber and the oil accumulating chamber; the inside of the sealed chamber is provided with a valve member which is arranged to open the flow adjusting hole in the separating plate when the ambient temperature exceeds a predetermined level and to close the same when the ambient temperature falls below a predetermined level in association with transformation of a thermosensitive body provided on the front surface of said cover, said transformation occuring in accordance with the change in the ambient temprature; an effective oil contact area in a gap portion for transmitting torque which is disposed between the surface of the case and cover and the surface of the driving disc, the surface opposing each other at the outer periphery of said driving disc is increased or decreased in order to control the torque transmission from the rotational shaft to the follower side of the sealed chamber, the thermal response type fluid coupling device being characterized in that an idle oil accumulating chamber which is connected to an introducing gap that is connected to the torque transmission chamber is provided at an outer position over a dam in the radial direction in said sealed chamber side and oil introducing means which is arranged to communicate the oil accumulating chamber and the torque transmission chamber only when the engine is stopped is provided in the separating plate. Furthermore, the device according to the present invention is characterized in that the oil introducing means is a circular penetrating hole disposed at a central position of the separating plate or a plurality of penetrating holes disposed on the same circumference of the axis of the separating plate.
The device according to the present invention is further characterized in that a sub-dam is provided in the vicinity of an inlet port of the circulated passage adjacent to the dam and the sub-dam is formed by a projecting wall which in part encloses a portion of said introducing gap on the side corresponding to the rotational direction and/or projecting wall projecting radially in the idle oil accumulating chamber.
The device according to the present invention is further characterized in that an inner space separating annular wall of the idle oil chamber is formed in such a manner that projections over the case and the cover are engaged with each other with a required gap remained for the introduction of oiland the gap for introducing oil comprises a gap disposed in the substantially axial direction and a gap disposed in the circumferential direction, and an exterior wall of the gap in the circumferential direction is formed in substantially the same plane as an inner wall of the outer periphery of the cover and the case, and the exterior wall of the gap in the circumferential direction has a tapered plane facing outwardly or inwardly. The gap disposed in the circumferential direction has a width larger than the distance beween the outer surface of the driving disc and the inner surface of the cover or the case.
The thermal response type fluid fan coupling device is further characterized in that the annular separating wall which forms the idle oil accumulating chamber is provided with at least one hole that is connected to the idle oil accumulating chamber. The device is further characterized in that the outer walls of the gap for introducing oil and the connecting hole which are axially disposed are formed in substantially the same plane as the inner wall at the outer periphery of the case and the cover. The device is further characterized in that the gap for introducing oil and the connecting hole have a tapered surface on the inner edge or outer edge thereof, and the width of each of the gap for introducing oil and the connecting hole is arranged to exceed the distances between the outer surface of the driving disc and both the inner surface of the case and the inner surface of the cover.